1. Field of the Invention
This invention relates to a new and simplified arrangement of a stuffing box assembly which is discussed herein in particular application to pumps having reciprocating or rotary pump rods but which is also applicable to any situation where an actuating rod or shaft penetrates through a wall and into a chamber containing a fluid, particularly an environmentally hazardous fluid under pressure. The present invention concerns a stuffing box assembly having an internal pressure transmitter piston used to equalize the pressure across the secondary seal in a stuffing box for reciprocating or rotating rods of pumping systems and to transmit the pressure of the fluid being pumped to a sacrificial safe-lubricant so the primary seal will be sealing a fluid of known characteristics. More particularly, the present invention is directed to reciprocating multiplex plunger pump stuffing boxes which include axially spaced primary and secondary seals that are separated by an annular chamber which contains a safe, refined, and clean lubricating fluid, such as a food grade hydraulic fluid. Even more particularly, the present invention concerns a stuffing box assembly having primary and secondary seals within a housing, with a safe lubricating fluid reservoir within the housing and arranged to contain a safe lubricating fluid therein at a pressure slightly exceeding the suction pressure of the pump, so that the secondary seal is substantially hydro-balanced with respect to suction pressure and both the primary and secondary seals are exceptionally well lubricated, thus permitting the packing assembly to have exceptionally long service life and to prevent leakage of pumped fluid to the environment.
2. Description of the Prior Art
One of the greatest sources of pollution of toxic fluids is the result of packing seals leaking when attempting to seal hazardous fluid under pressure. All plunger pumps used to transfer, load, circulate liquids, or produce oil wells with hydraulic pumps have, at one time or another, had to have the packing seal assemblies replaced because of leakage of the fluid being pumped due to wear to or damage of the packing seal assemblies by the pumped fluid. More and more oil wells are being produced with hydraulic pumping systems, and the horsepower requirements increase as the wells get deeper. As the pressure increases, the life of packing seals and pump plungers decreases. The application of this technology to multiplex plunger pumps as used in hydraulic pumping systems for producing oil wells will overcome the universal problem of losing production and polluting the area around the pumping unit.
In recent years progressive cavity pumps (P.C. pumps) have been developed for producing oil wells using rotating sucker rods. In P.C. pumping systems the stuffing box packing seals do not receive any lubrication from the fluid being pumped because the polished rod is rotating in the stuffing box instead of reciprocating, as compared with beam type pumping units, where the polished rod strokes down into the fluid being pumped. The greatest problem and maintenance requirement in P.C. pumping systems is controlling the leakage of produced fluid through the stuffing box seal around the rotating polished rod due to lack of lubrication, causing heat. The present invention helps solve the this problem in P.C. pumping systems, because the packing seals are pressure lubricated with clean refined fluid of known characteristics, and because hydro-balance is provided across the secondary seal. Maintenance cycles are greatly extended and no produced fluid will leak to the environment when the primary packing seal begins to leak.
The concept of hydro-balancing the pressure across the secondary seal of a stuffing box is the subject of U. S. Pat. No. 5,209,495 which is embodied in a commercial product for reciprocating sucker rod pumping systems. However, this patented technology has the pressure transmitter as a separate component of the stuffing box with the transmitter piston functioning in its own housing or cylinder.